Resilient mount for magnetic heads



NOV. 18, 1952 CAMRAS RESILIENT MOUNT FOR MAGNETIC HEADS 5 Sheets-Sheet 1 Filed Aug. 30, 1947 MIM w 6mm;

Nov. 18, 1952 I M. eAMRAs 2,618,710

RESILIENT MOUNT FOR MAGNETIC HEADS Filed Aug. 30, 1947 3 Sheets-Sheet 2 H E? x 62 49" I 5 Fl I 50//46/ If? J! Mae/m (Xv/Pi:

Nov. 18, 1952 M, CAMRAS RESILIEN'I' MOUNT FOR MAGNETIC HEADS Filed Aug. 30, 1947 3 Sheets-Sheet 3 jig- 7225.27 0.2" Mmew/v C Eve/ 29' Eris.

Patented Nov. 18, 1952 UNITED STATES PATENT OFFICE 2,618,710 B SiLlIENTMQ ii f F Q ET HEADS Marvin (lamr'as, Chicago, Ill., assignor to Armour Research Foundation of Illinois Institute of Technology, Chicago, Ill., a corporation of Illinois 7 Application Augu t so, 1947, Serial No. 771,492

- This; inventionrelates to magnetic recording and;reproducing apparatus, and more'particularlyrto a magnetic sound projector for motion pictures.

The use of a magnetic sound track on a moving picturefilm has-been known for some-time, and many suggestions have been made as to how it might 'be used-in; a motion-picture projector so thatthe soundtoaccompany themoving picture niiglhtbe reproduced from a magnetic sound track rather'thamfrom an optic-sound track as is the common" practice of the present day.

W-hilemany suggestions have been made, none of the known systems to date have been practical" ducing headandmounting'therefor, j

-- 'A-further; object; of the ipres'ent invention is reproducing headgwx provideqa'novelmethod' for shielding a magnetic --A-nother and further object of the presentin -I invention is to provide novel magnetic sound {lick-111p arrangement-whicnis vextremely small in constructionwhich is highly efiicient in operatiopi. and :which is particularly effective when employedin conjunction with 8 mm. and 16 mm. movi ng-picturefilmi Another and still further object of the presentinvention is to provide'a' novel 'magneticjsound' and movingpicture projectors'having both magnetic and optic sound reproducing means:

'- -'Ijhenovel-features--which'I believe to be char-,

acte'ristic'- -of my'invent-ion are set-forth with, par= ti'cularity in-the appended claims: My invention itself -'howeve'r both as to its organization;

metho d of; operation, and manner of construction; together with further-"objects and advantages,"

may best -bei nderstood by reference to the accompanying drawings in which netio-"sound and -m'otion-picture -projector' with; a portionitofi each of the two' reels broken-away) and which embodies certain of the novel-prin ciples and teachings of the present invention.

record made on a motion 2 Claims. (01. 179-1002) a I Figure- 11=is a vfron'televational view of amag- Figure-'2 is a greatly enlarged elevational view of the 'film drive mechanism immediately below the lens.

Figure 3 is a still further enlarged sectional view through the reproducing head housing and mounting, as taken along the line III-III of Figure 4;

Figure 4 is a bottom view of the reproducing head mounting and housing.

Figure 5 is a greatly. enlarged fragmentary view of the recording head core as the film passes over the rotary stabilizer.

Figure 6 is a diagrammatic illustration of a piece of film withboth a magnetic sound track thereon and an optic sound track thereon.

Figure 7- is a greatly enlarged sectional view of the film shown in Figure 6 as taken along the line VII-VII of Figure 6. v

Figure 8 is .a sectional view taken along the line VIIIVIII of Figure2. v

Figure 9 is a view similar to Figure 2, but illus trating a modified form of the present invention wherein the reproducing head is mounted directly below the rotarystabilizer.

The sound projector l0 illustrated in Figure 1 of the drawings includes a main housing I l which includes the motor for driving the various mov-V able mechanical elements of the system, the audio amplifier for the sound, system, and other conventional parts of a moving picture projector.

-The housing It also includes a supplemental housing l2 which contains the projection lamp. Mounted on the forward part of the housing H are apair of removable reel arms [3 and [4 which are secured to the main frame of the machine by lock screws 1:5 and I6, respectively. 4

The main lens I! is mounted at the front of the gate mechanism .18. The supply reel 19- ismounted ona spindle 20, while a take-up reel 2| is mounted ona spindle. 22. The spind1e-22 isdriven through an endless loop drive member (not shown) mounted within the arm I3. H

The movingpicture film 23, as shown, is beingunwoundfrom the supply reel l9 and wound-up on the take-up reel 2|; The film 23 passes over a sprocket wheel 24, which is driven at a substan tially constant speed andthen passesthrough thegate mechanism I8. It then. passes back .in a half-loop over a. roller- 25 and then down around a rotary stabilizing element 26. After, leaving the rotary stabilizingpelement 26, it passesv up over a sprocket wheeljlidowin lover astripper stud28 and over'a. guide roll 29. The film,- in

passing over the roller '25, is held in place by two small rollers 30 and 3|. The film 23 in passing over the rotary stabilizer 26 is held in place by a tension roller 32 which is carried on the arm 33 hinged about the aXis of rotation of the roller 25.

The tension roller 32 is spring-biased (not shown) in a counter-clockwise direction about its pivot point, thereby to cause the tension roller 32 to be constantly urged against the rotary stabilizer 26.

The rotary stabilizing element 26 is mounted on a shaft 34 and is either of substantial mass itself, thereby to act as an inertia member, or else has an additional inertia member (not shown) mounted on the shaft 32 within the housing H. The shaft 35 is a freely rotating shaft,

and hence the rotary stabilizing element 26 is 4 in Figure 6, and a still further sectional enlargement appears in Figure 7.

As shown in Figure 6, the film 23 includes a row of sprocket holes 58 going down one side of the film in a position located between the picture frames 59 and an outer edge of the film. A magnetic sound track 60 is placed between the sprocket holes 58 and the adjacent-edge of the film. This sound track 60 may be. formed of powdered ferromagnetic material having relatively high coercive force which is bonded or otherwise suitably secured to the surface of the driven by the film 23 as it rides thereon. The

magnetic sound head engages the sound track of the film 23 as it passes over the rotary stabilizing element 26. This insures substantially constant linear speed of the film sound track as it passes the recording and reproducing head.

As may be seen best in Figure 2 of the drawings, the sound head assembly 35 is mounted on a shoulder formation 36 which lies below the retary stabilizing element 26.

' As may be seen best in Figures 3 and 4 of the drawings, the sound head assembly 35 includes a housing 37 which is mounted on an arm 33 which is bolted or riveted as at 39 to the. shoulder formation 36 of the housing. The housing 37 and the arm 38 are preferably made of steel or other suitable magnetic material so as to act as a shield for the head 46 whichis mounted within the housing 31. The head 46 includes a core member 4| having two confronting leg portions 62 and 43 which terminate in closely spaced confronting relationship to each other to define a gap is. A signal coil 5 is Wound on the core H and connects through leads 46 and 41 to the amplifier (not shown).

The head 43 is mounted on a lon fiat leaf spring t8 which is supported at one end between blocks 49 and 50. A third block 5| also holds in place a second leaf spring element 52 which bears against the spring 43 and acts as a dampening element as well as to stiffen its action somewhat. This, of course, takes place as a result of the sliding friction of the downturn end of spring 52 against sprin 48 when spring 38 is flexed.

The lower side of the housing 31 is, of course, covered by the mounting plate 38 and includes an off-set portion 53 which is provided with an opening 54 through which a small portion only of the core 2 l of the head to projects.

As may be seen best in Figure 4, the opening.

54 is only slightly larger than the le portions 42 and 43 of the core 4| which projects therethrough. It will thus be seen that the head on its leaf. spring or cantilever spring mounting 48 is free for limited movement but is prevented from damage from sudden blows since the head 40 is protected from top blows, side blows and end blows-by housing 31, and bottom blows are restrained by the'member 38 after a relatively small movement of the head All. It will further be observed that the head i!) is magnetically shielded'by-the housing 31 from stray magnetic fields such as might be present from the drive motor of the projector unit. 2 g

'The pole portions 42 and 43, as may be seen best in Figure 5, are slightly concave over their lower surface as at 55 and 56 so as to conform to the curvature of the'cylindrical surface 57 of the rotary stabilizing element 26.

The film 23 is illustratedin'an enlarged view film 23 opposite to that which carries the emulsion 6| (see Figure 7).

The head bears against the magnetic sound track 660i the film 23, as the film 23 rides over the rotary stabilizer 26. It is maintained in firm but constant contact with the sound track 60 by virtue of the resiliency of the spring arm 58, and if any irregularity occurs on the film, the head 40 merely rides over the irregularity due to the shape of the ends of the leg portions 42 and 43 and the manner in which they are mountedv on the spring arm 48. Any movement of this character which occurs is damped by the damping spring 52.

The projector It) also includes means for the optical reproduction of sound. The filmf23 as shown in Figure 6 of the drawings includes theusual optical sound track 6| which lie along theopposite edge of the film 23 from that in which the magnetic sound track 60 is disposed. The optical sound track 6| is on the portion of the film 23 which overhangs the rotary stabilizing element 26 as shown in Figure 8 of the drawings.

In Figure 8 of the drawings, the film has been broken away where it wraps partially around the rotary stabilizing element 26. The light transmitting' element 62 of theprojector l0 trans-- mits light from the lamp 63 after it passes through the sound track portion6l of the film to the light-sensitive element (not shown) which is located at the opposite end of the member 62. Interposed between the lamp 63 and the film 23 is another light focusing and transmitting member 64.

The particular details of the optic end of the present system are only diagrammatically illus-.

trated, since the details of this phase of the projector may be any conventional optical sound system, it being remembered that it is the combination of this optical sound system with the magnetic sound system which forms one of the features of the present invention.

While I have shown a particular embodiment of my invention, it will, of course, be understood,

' that I do not wish to be limited thereto, since many modifications may be' made, and IQtherefore, contemplate by the appended claims to cover all such modifications that fall within the true spirit and scope .of myinvention. w J I I claim as my invention: 7 l 1. In combinationwith a motion picture'projector arranged for reproducing sound from a film having a magnetic sound track, meansfor imparting a constant speed to said film through. said'projector, a rotary -.stabi lizing elementfipni said projector over which said film rides, an electromagnetic transducer head in resilient engagement with said sound track, said transducer: head including a pairof confronting pole por tions, a spring member urging said poleporti'ons into contact with said sound track; and a second spring member engaging said first spring tOi dampen the vibrations of said head uponjcon-w 5 tacting irregularities in the film as the film rides over said stabilizer.

2. In combination with a motion picture proiector arranged for reproducting sound from a film having a ferromagnetic sound track, means for imparting a constant speed to said film through said projector, a rotary stabilizer on said projector over which said film rides, a pinch roll holding a portion of said film against said stabilizer, an electromagnetic transducer head in resilient engagement with the sound track, said transducer head including a housing having an opening therein opposite said stabilizer, a pair of confronting pole portions freely extending through said opening, a leaf spring urging said pole portions into contact with said sound track, and a second spring member engaging said first spring to damper the vibrations of said head when said pole portions contact irregularities on the film as said film rides on said stabilizer.

MARVIN CAMRAS.

REFERENCES CITED The following references are of record in the file of this patent:

6 UNITED STATES PATENTS Number Plumber Name Date Morin Sept. 1, 1908 Chipman Dec. 28, 1926 Kuchenmeister June 2, 1931 Kellogg Oct. 13, 1931 Kuchenmeister Sept. 13, 1932 Cohen Mar. 6, 1934 Gillet Apr. 21, 1936 Simons May 26, 1936 Zillger Sept. 21, 1937 Begun Nov. 28, 1944 Conant Nov. 5, 1946 Camras Apr. 8, 1947 FOREIGN PATENTS Country Date Norway May 28, 1945 Great Britain Mar. 16, 1933 Great Britain Feb. 7, 1936 France Nov. 20, 1940 

